Pollutants and/or heavy metals, for example a phosphate pollution, are found, for example, in aquarium water and pond water. Phosphate ions are introduced via the fish food and via discharges into the water, which causes severe algal growth. If it is wished to prevent this it is necessary to change the water regularly which, in particular in the case of seawater aquaria, leads to considerable costs, or to remove phosphate from the water using absorbers.
An elevated arsenic content is met, for example, in some groundwater sources.
Previously known processes for removing pollutants and/or heavy metals such as phosphate, arsenic and some other ions from flowable media such as water are based on the adsorption to various substances, or ion exchange.
Commerce offers granulated products which are introduced into water filters. An effective product has proven to be, for example, granulated iron hydroxide, as described in DE-A 4 320 003. JP 08089951 describes filters packed with aluminium hydroxide or iron hydroxide. In this case, the used adsorber must be replaced after the service life. Sufficient porosity of the filter material is of importance here to ensure sufficient through-flow, the packed height of the adsorber layer having an effect on the through-flow velocity of the water.
The inventors of the present invention recognized that disadvantageous here is the laborious handling of loose filter materials and the turbidity of the water due to finely divided filter breakthrough which is produced on first filling and change of adsorbate. The abovementioned JP 08089951 describes, for example, the workup of sludge.
U.S. Pat. No. A1 5,124,044 describes a process for impregnating sponges with iron chloride and ammonia solution to precipitate Fe(OH)3 in the sponge. This reaction, however, can be controlled only with difficulty in practice. JP 06277504 presents the production of an absorber by mixing microparticles with a gel and subsequent dewatering.